US Patent 7284024 Quantum noise random number generator

A quantum noise random number generator system that employs quantum noise from an optical homodyne detection apparatus is disclosed. The system utilizes the quantum noise generated by splitting a laser light signal using a beamsplitter having four ports, one of which receives one of which is receives the laser light signal, one of which is connected to vacuum, and two of which are optically coupled to photodetectors. Processing electronics process the difference signal derived from subtracting the two photodetector signals to create a random number sequence. Because the difference signal associated with the two photodetectors is truly random, the system is a true random number generator.